Embodiments of the present invention relate to a substrate support assembly for supporting a substrate in a process chamber.
In the manufacture of electronic circuits, such as for example, integrated circuits and displays, a substrate is placed in a process chamber and a process gas is introduced into the chamber to process the substrate. The process chamber generally comprises an enclosure wall surrounding a substrate processing zone. A gas energizer energizes process gas introduced into the chamber by applying RF or microwave energy to the process gas, for example via a microwave applicator, an inductor coil or electrodes arranged about the chamber. The process gas is energized to perform processes such as an etching process to etch features in the substrate or a deposition process to deposit a layer of material on the substrate.
During processing of the substrate in the process chamber, the substrate is held on a substrate support assembly. The substrate support assembly comprises a support having a substrate receiving surface. The assembly can also have an electrode that serves as part of the gas energizer to energize the process gas. The support electrode may also optionally be electrically biased to electrostatically hold the substrate on the support assembly. The assembly can have electrical connectors and conducting structures such as wires or leads. The electrical connectors connect portions of the support assembly to other chamber components or external circuitry. For example, the substrate electrode can have an electrical connector that electrically grounds (ground connector) or provides electrical power (power connector) to the support electrode. The ground connector maintains the support electrode at an electrically grounded potential while a wall electrode in the chamber is electrically biased to energize a gas in the chamber to process the substrate. The ground connector can also dissipate unwanted charge from the support assembly to facilitate removal of the substrate from the support. Another example of an electrically conducting wire is a thermocouple, which is used to monitor temperatures during processing of the substrate. Other connectors can include electrical wires connected to process monitors.
One problem with conventional substrate support assemblies arises when electrical arcing and glow discharges occur between the plasma in the chamber and the connectors and wires in the support. For example, electrical arcing can occur when energized process gas corrodes the insulator coating on a connector or thermocouple. The electrical potential applied to energize the gases in the chamber can also cause glow discharges or micro-arcing. Additionally, when electrically conducting wires pass close to charge carrying wires, back e.m.f. that is induced in the wires can cause arcing and signal cross-talking. Such electrical arcing and glow discharges are undesirable because they damage or “burn” the connectors or wires and adjacent portions of the substrate support. In some plasma environments, degradation of the substrate support assembly and its components can require their refurbishment or replacement after processing of only a relatively small number of substrates, which increases fabrication costs per substrate.
The energized process gases in the chamber can also corrode portions of the substrate support assembly, which eventually leads to contamination of the substrates being processed and failure of the support assembly. For example, energized process gases such as halogen gases can erode metal portions of the support assembly, such as its aluminum portions, requiring frequent cleaning or replacement of these parts.
Thus, it is desirable to have a substrate support assembly that exhibits reduced electrical arcing or glow discharges in a plasma environment. It is also desirable to have a substrate support assembly that allows processing of a large number of substrates without frequent replacement or repair. It is further desirable to be able to easily refurbish or clean the substrate support assembly components.